Energy sources
C.1 Energy sources (3 hours)
Pause for thought
This sub-topic looks at different energy sources and their efficiency in actually providing the energy required for society, as it currently exists, to function. It is a sobering thought that when we turn on a traditional incandescent 60W electric light bulb less than 1% of the raw energy consumed is actually converted into light. It has been calculated that it requires 200-300 kg of good quality coal to power just one 60 W light bulb for one year. 99% of the raw energy is wasted in the supply chain. If the raw source is a conventional fossil fuel then 10% of the energy is lost during combustion. Of the 90% that is transferred to steam to drive the steam turbine only 40% is transferred into mechanical energy and a further 2% is lost in converting this into electricity. The transmission of electricity through the grid system from the power station to the consumer’s home loses a further 10% and the incandescent light bulb itself is particularly inefficient converting only about 2% of the received electrical energy into light.
Image from Electropaedia
What this demonstrates is that while it is important to use more renewable sources to minimise climate change etc. in the future, the most significant change required is to make the transfer of energy from the raw source to the end user as energy efficient as possible.
Nature of science
Energy has both quantity and quality. The energy changes in the world around us are as a result of potential and kinetic energy changes at the molecular level.
Learning outcomesAfter studying this topic students should be able to: Understand:
| Clarification notesNo specific clarification notes are given for this sub-topic. International-mindednessThe International Energy Agency (IEA), an autonomous organization based in Paris, works to ensure reliable, affordable and clean energy for its 29 member countries and beyond. The International Renewable Energy Agency (IRENA), founded in 2009, is based in Abu Dhabi, UAE. It works to promote the widespread adoption and sustainable use of all forms of renewable energy, including bioenergy, geothermal, hydropower, ocean, solar and wind energy in the pursuit of sustainable development, energy access, energy security and low-carbon economic growth and prosperity. |
Teaching tipsThis sub-topic can really be divided into two main strands - a general discussion on different energy sources and how they are used and then some specific calculations for different energy sources. You could get students to research individually or in groups and then report back on the advantages and disadvantages of all the different energy sources - both current and possible future sources. Distinguish between renewable and non-renewable sources and emphasise the importance of energy efficiency and how some of the energy available to do work is always lost as heat when energy is converted from one form into another form. Then provide examples for students to compare different energy sources quantitatively by calculating the energy densities, specific energies and the efficiency of energy transfer. Although three hours are allocated for this sub-topic in reality much of it overlaps with the specific types of energy sources covered in the remaining sub-topics of this option. | Study Guide
Page 141 QuestionsFor ten 'quiz' questions (for quick testing of knowledge and understanding with the answers explained) see MC test: Energy sources. For short-answer questions see Energy sources questions together with the worked answers on a separate page Energy sources answers. Vocabulary listrenewable energy |
Teaching slides
Teachers may wish to share these slides with students for learning or for reviewing key concepts.
Other resources
1. Ten future energy sources that can replace fossils fuels.
2. Energy efficiency - how we can get more from less.
3. A useful site from Energy4me comparing the pros and cons of different energy sources.